A 240-million-year-old fossil is now the oldest known ancestor of snakes and lizards -- and experts are calling it a 'Rosetta Stone' of evolution

Davide BonadonnaA life scene in the Dolomites region, Northern Italy, about 240 million years ago, with Megachirella wachtleri walking through the vegetation.

Scientists have determined that a lizardfossil discovered in 2003 is240 million years old – making it the earliest known lizard fossil ever discovered.

Researchers also determined that the creature is the world’s earliest known ancestor of snakes and lizards.

The fossil’s age means that lizards coexisted with dinosaurs for millions of years, which contradicts what researchers previously thought.

Scientists have discovered a 240-million-year-old fossil that is thought to be the world’s earliest known ancestor of snakes and lizards.

The fossil, from the species Megachirella wachtleri, was first found in 2003 in Italy’s Dolomites mountain range, but it had not been accurately dated.

A group of researchers from the University of Alberta in Canada, the University of Bristol in England, and a number of other institutions recently dated the fossil to 240 million years old. That’s around 75 million years older than the earliest known squamate (a group of lizards, snakes, and worm lizards).

The finding, which was published in the journal Nature on Thursday, means the first lizards were living on Earth before the Permian-Triassic extinction period – much earlier than previously thought.

The ‘Rosetta stone’ of lizard evolution

Though only a few inches long, the stubby Megachirella is perhaps one of the most important lizard fossils ever studied.

After dating the fossil, researchers debated whether the Megachirella fossil was actually a true lizard because of its surprising age. To find out, the study’s authors conducted a CT scan of the fossil. Its head, wrist, and shoulder features matches up with those of modern reptiles, which bolstered the researchers’ confidence that they had found the earliest example of a lizard.

Scientists now believe the world’s first lizards evolved over 250 million years ago, a timeline revision that could provide a wealth of information about how lizards evolved.

“Fossils are our only accurate window into the ancient past,” Michael Caldwell, one of the study’s co-authors, said in a statement. “Our new understanding of Megachirella is but a point in ancient time, but it tells us things about the evolution of lizards that we simply cannot learn from any of the 9,000 or so species of lizards and snakes alive today.”

Before the Megachirella discovery, scientists were unsure how and when ancient lizards evolved into their modern-day counterparts. The Megachirella could be the key to unlocking the process of reptilian evolution – Caldwell compared its significance to the Rosetta stone in a video released by the MUSE Science Museum in Italy, which was involved in the study.

“The specimen is 75 million years older than what we thought were the oldest fossil lizards in the entire world and provides valuable information for understanding the evolution of both living and extinct squamates,” Tiago Simões, the study’s lead author and a PhD student at the University of Alberta, said in a statement. He added: “It is extraordinary when you realise you are answering long-standing questions about the origin of one of the largest groups of vertebrates on Earth.”

To learn more, check out this video released in May describing the Megachirella find, from the MUSE Science Museum: